Stiffening member for shoes and the like



Patented Oct. 26, 1943 UNITED STATES STIFFENING MEMBER FOR SHOES AND THE LIKE

Paul R. Austin, Wilmington, Del., and Quentin L. Quinlivan, East Orange, N. 1]., assignors to The Celastic Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Application December 13, 1941, Serial No. 422,926

6 Claims.

This invention relates to stiffening members for shoes and the like, and more particularly, to box toes and. counters of heat-softening type.

Material for stiffening members is commonly made by impregnating a suitable fabric with a thermoplastic material or mixture of materials. Blanks of suitable size and shape out from the impregnated goods, and usually skived to a tapered edge, are shaped into conformity with the last of a shoe by being softened by heat and, while still soft, stretched in place over the last. Stifiening materials of this type may be designated as heat-softening, to distinguish them from those which are softened for lasting by being nary means, such as steaming, should retain their softness for a time suiiicient to permit lasting, and, as apart of the structure of the finished shoe, should not be subject to deformation by heat in the course of ordinary wearing, storage and display.

Satisfactory shoe stifiening material must be capable of withstanding the usual machining operations, must be sufiiciently adhesive when hot to make the use of an auxiliary adhesive unnecessary, and ordinarily must cause no stain. .It is essential that the material shall have adequate rigidity and toughness without being excessively thick. Further requirements are that the material shall not be subject to deterioration with age, nor to damage either by immersion of the shoe in water or by protracted contact with moisture or with perspiration from the feet of the wearer.

An'pbject of the present invention is to provide improved stiffening material of the heat-softening type. More specifically, it is an object of the invention to provide such a/material present- R representing a saturated divalent aliphatic hydrocarbon radical of six to ten carbon atoms, inclusive, dibasic acids of the formula HOOCR-'-.COOH R representing a saturated divalent aliphatic weight.

Especially valuable as impregnants are polyester-polyamides selected from the group comprising (1) that derived from decamethylene diamine, ethylene glycol and sebacic acid, with 10 ester-forming ingredients in amount between 85 and 100%, and preferably about 95%, (2) that derived from hexamethylene diamine, ethylene glycol and sebacic acid, with ester-forming ingredients in amount between 85% and 100%, and

preferably about 95%, (3) that derived from hexamethylene diamine, ethylene glycol and adipic acid, with ester-forming ingredients in amount between 82% and 95%, and preferably about 85%, and (4) that derived from hexamethylene diamine, propylene glycol and sebacic acid,

with ester-forming ingredients in amount between 85% and 95%, and preferably about 90%.

0 the solution, removing the fabric, thus impregnated, from the solution and stripping from its surface the excess of the solution carried thereon, and heating the fabric, thus impregnated and stripped, to remove volatile solvent therefrom.

a The invention embraces the foregoing mate-- .rials as impregnants, the resulting impregnated fabrics, and blanks and heat-shaped stiffening members made therefrom.

The impregnants utilized in the present invention are of the type disclosed in U. S. Patent No.

2,224,037, issued December 3, 1940, to Brubaker, Christ and Cofiman, and are prepared by heating at reaction temperature certain mixtures of diamines, dibasic acids and glycols, and by continuing the heating until the polymers obtained are capable of being formed into continuous filaments. In this preparation of these impregnants, the proportions of starting ingredients will have been chosen to provide the desired percentage of ester, whichjterm, used herein as in the patent referred to, applies to the weight ofingredients taken and not to the percentage of ester in the completely polymerized product. The heating of the intermediate polymer will have been conducted, as described in the patent, in

such manner as to lead to the formation of a final polymer having fiber-forming properties.

It will be obvious that when, in accordance with the invention, the percentage of ester-forming ingredients is selected at 100, th product will be a polyester rather than a polyester'polyamide. Such a polyester constitutes the limiting case of a series of polyester-polyamides in which the percentage of amide-forming ingredient is progressively diminished.

Polyester-polyamides derived from saturated aliphatic straight chain diamines of from six to ten carbon atoms, inclusive, glycols of from two to three carbon atoms, inclusive, and saturated aliphatic straight chain dicarboxylic acids of from six to ten carbon atoms, inclusive, with esterforming ingredients in amount between 80% and 100% by weight of the whole, have been found to have satisfactory softening characteristics for use as impregnants in shoe stiffening material. Based on the softening point test outlined below, they exhibit softening points within the range of about 50 C. to about 110 C. Material impregnated with these polyester-polyamides is made pliable by being heated on a steamer," which is a box or tray with a perforated'bottom set over a bath of boiling water, retains its pliability for a. period of time sufficient to permit lasting and yet, as a part of the finished'shce, withstands all the variations in temperature to which footwear is normally subjected.

The softening point determination is made on a brass block having its two broad faces parallel and provided on a side with a long horizontal depression for the reception of a thermometer. Preferably the depression is placed about three millimeters below the upper face of the block and is of suificient depth to permit the thermometer to be inserted far enough to avoid the necessity of any stem correction. The block is placed on a support and heated rapidly to within approximately 20 degrees of the predicted softening point. The rate of temperature rise is then adjusted to approximately five degrees per minute. A thin film of the material to be tested is brought into contact with the block at definite temperature intervals with the application of light pressure, conveniently by means of a small metal spatula. Fresh sections of film are used for each trial. Another-series of tests is similarly made at intervals while the block is cooling from a temperature above the softening point. The softenin temperature is-usually taken as the range between the' temperature at which the film Just begins to stick to the block during heating and the temperature at which the film just ceases to stick during cooling.

For satisfactory use, stiffening material for shoes must be capable of being blanked and skivedwith'out raveling, tearing or gumming. In being pulled over the last it must not tear. As a part of the shoe, it must provide adequate rigidity and toughness in proportion to thickness.

The polyester-polyamides with which this invention is concerned have a hardness of from 11 to 80, as measured by the Pfund-hardness determination described below. Heat-softening shoe stiffeners incorporating these polyester-polyamides as impregnants provide rigidity and toughness without excessive thickness. They endure prolonged wearing and hard usage.

The test for hardness is based on the method described in Gardner's Physical and Chemical Examination of Paints, varnishes, Lacquers and Colors, Ninth Edition, 1939, page 118. The apparatus consists of a brass beam pivoted near one end which is provided on the long arm side of the pivot with a quartz cylinder and a series of weights so positioned that the distance from the pivot to a point on the beam directly below the center of gravity of the weights is exactly twice the distance from the pivot to the center of the rod. A weight on the short arm is ad- Justed to balance the long arm and quartz cylinder with the Weights removed. The quartz cylinder terminates at its lower end in a hemisphere of /4. inch diameter and is so arranged that weights applied to the beam will cause it to bear upon a film of the material to be tested while the beam is in a substantially horizontal position. A reflector and a microscope provided with a micrometer eyepiece are mounted directly above the quartz cylinder.

In making a hardness determination a film of the material to be tested is applied to'the upper side of an inflexible horizontal plate beneath the cylinder and successively increasing loads are applied to the cylinder by means of weights on the long arm of the beam. The diameter of indentation produced under each successive load is measured by the eyepiece micrometer, the region of contact of the hemispherical end of the cylinder with the film appearing, when viewed through the microscope, as a dark disc. That force which exerted by' the cylinder on th film will produce an indentation contact area having a diameter of 0.32 millimeter, measured while the cylinder is in contact with the film, is taken as the hardness of the material. The force exerted by the cylinder is twice the weight applied to the end of the long arm of the beam. The force corresponding to an 7 peratures, they are applied in solution at somewhat elevated temperatures.

Preferably the impregnant is put into solution at the boiling point of the solvent, 1. e. by

heating the impregnant and the solvent together in a vessel fitted with a reflux condenser.

Impregnation is effected preferably in continuous manner, by passing the fabric through the hot solution of impregnant and thence between warm stripper members, conveniently metal bars. which are close enough together to strip off, and return to the bath, the excess of solution over that required in the fabric. The material is then seasoned for removal of solvent. Fabric thus impregnated bears about 300 to about 900 parts by weight of polyesterpolyamide per parts of fabric.

Suitable volatile solvents for the polyesterpolyamldes will include ethyl acetate, butyl acetate, ethyl alcohol, isopropyl alcohol, cyclohexanol, cyclohexanone, diisopropyl ketone, and mixtures thereof.

Suitable porous fabrics which may serve as bases for the impregnated stiffening materials of the present hivention include felt, paper, flannel, canvas, duels felted cellulose fiber, such as that sold under the name Krafelt, and the like.

The following examples, in which all proportions are given by weight unless otherwise stated, illustrate the manner of preparation and use of the impregnated products of the invention:

Example I The impregnant used is a polyester-polyamide derived from decamethylene diamine, ethylene glycol and sebacic acid in such proportions as to provide 95% of ester-forming ingredients. This is dissolved in its own weight of a mixture oi. ethyl acetate and ethyl alcohol, 85:15, by being heated therewith under reflux.

A napped cotton flannel weighing 6 ounces per square yard is passed into the resulting impregnating solution, maintained at 60 C., and thence immediately between warm iron rods spaced 0.072 inch apart. The impregnated flannel is then dried at 105 0., and upon completion of this removal of solvent contains 490-570 parts of impregnant per 100 parts of flannel, i. e., 83 to 85 parts per 17 to parts.

The finished stiffening material is well suited for use as box toes in women's shoes.

Example II A flannel weighing 10 ounces per square yard is impregnated in the bath of Example I, stripped between heated bars spaced 0.115 inch apart, and seasoned. The resulting stiffening material, containing 550 parts of impregnant per 100 parts of' flannel, is suitable for use as box toes in mens shoes.

Example III A polyester-polyamide derived from decamethylene diamine, ethylene glycol and sebacic acid in such proportions as to provide 86% of esterforming ingredients is dissolved, with the aid of heat, in its own weight of a mixture of ethyl acetate and ethyl alcohol, 85:15, and is used as an impregnant for a napped flannel. The load of impregnant is 860 parts per 100 parts of flannel.

Example IV A polyester derived from ethylene glycol and sebacic acid is dissolved, with the aid of heat, in its own weight of a mixture of ethyl acetate and ethyl alcohol, 80:20, and the resulting solutionis used to impregnate a. felt weighing 7 ounces per square yard. The load of impregnant in the seasoned goods is 760 parts per 100 parts of the felt.

Example V A polyester-polyamide derived from hexa methylene diamine, ethylene glycol and sebacic acid, in such proportions as to provide 95% of ester-forming ingredients, is dissolved, with the aid of heat, in its own weight of a/mixture of ethyl acetate and ethyl alcohol, 85:15, and is used as impregnant for flannel. The goods are stripped of excess of impregnating solution, and upon being seasoned contain 325 parts of impregnant per 100 parts of original fabric.

Example VI Example VII A polyester-polyamide derived from hexamethylene diamine, ethylene glycol and adiplc acid, in such proportions as to provide 85% of ester-forming ingredients, is dissolved, with the aid of heat, in its own weight of ethyl alcohol, and is used as impregnant for cotton flannel as described in Example I. The finished seasoned stiffening material contains 500 parts of impregnant per 100 parts of flannel.

Example VIII A polyester-polyamide derived from hexamethylene diamine, ethylene glycol and adipic acid, in such proportions as to provide 85% of ester-forming ingredients, is dissolved, with the aid of heat, in its own weight of a mixture of acetone, ethyl alcohol and water, 60:15:25 parts,

and is used as impregnant for cotton flannel as.

described in Example,I. The finished seasoned stiffening material contains 550 parts of impregnant per 100 parts of flannel.

Example IX A polyester-polyamide derived from hexamethylene diamine, ethylene glycol and adipic acid, in

such proportions as to provide 85% of ester-- Example X A polyester-polyamide derived from hexamthylene diamine, propylene glycol and sebacic acid,

. in such proportions as to provide 90% of ester- A polyester-polyamide derived from hexarnethylene diamine, propylene glycol and sebacic acid, in such proportions as to provide of .esterforming ingredients, is dissolved, with the aid of heat, in its; own weight of ethyl acetate. resulting solution, while still hot, is used to impregnate cotton flannel. The impregnated fabric is seasone to remove solvent, and in its dried condition ontains 650 parts of impregnant, per parts of flannel.

Example XII A polyester-polyamide derived from hexamethylene diamine, propylene glycol and sebacic acid,

' in such proportions as to provide 85% of esterforniing ingredients, is dissolved, with the aid of heat, in its own weight of ethyl alcohol. The resulting solution, while still hot, is used to impregnate cotton flannel in the manner described in Example I. The impregnated fabric i seasoned, to remove solvent, and in its dried condition contains 525 parts of impregnant, per 100 parts of flannel.

It will be understood that the above examples are merely illustrative and that the invention broadly resides in a heat-softening stiffening material for shoes and the like, comprising a porous fabric impregnated with a polyester-polyamide of the type herein considered, and the process of preparing such stiffening material. I

The impregnated fabrics of the invention are readily and satisfactorily blanked and skived by customary methods. Shoe-mailing members The made in accordance with the invention are prepared and built into the shoe in standard manner and give satisfactory service. Upon being placed in the steamer, following the standard practice, the blanks become completely limp and soft, sticky enough to adhere to the shoe lining but not sticky enough to adhere to the operators fingers. The limpness is retained, upon removal from the steamer, for a period entirely adequate to permit of the stretching of the blank over the last. The construction of the shoe is carried on in the usual manner, and neither at this stage nor later, during the wearing of the shoe, does the impregnant exert any staining or other deleterious effect upon the leather or fabric with which it may be associated in the shoe.

stiffening members made in accordance with the invention possess unusual rigidity and toughness in proportion to thickness, and are accordingly adapted to provide adequate stiffening and support without undesirable bulk.

They do not deteriorate with age nor as a result of exposure to heat, moisture and perspiration incidental to prolonged hard wear. Also, they are waterproof in the ordinary sense of being undamaged by brief or prolonged immersion in water at ordinary temperatures.

While the principal use now contemplated for the invention is in connection with the manufacture of shoes, it will be obvious that it will be applicable in other fields also, including, for example, the manufacture of protective equipment for athletes, sportsmen, artisans, etc., the stiffening of articles of clothing other than shoes and, in fact, in the preparation of rigid or semirigid structures of great variety.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. A heat-softening stiffening member for shoes and the like, said member comprising a porous fabric impregnated with 300% to 900%, by weight of said fabric, of a polyester-polyamide derived from the inter-reaction of a diamine of the formula NH2RNH2, R representing a saturated divalent aliphatic hydrocarbon radical of six to ten carbon atoms, inclusive, a dibasic acid of the formula HOOC-R'COOH, R representing a saturated divalent aliphatic hydrocarbon radical of four to eight carbon atoms, inclusive, and a glycol having two to three carbon atoms, inclusive, per molecule, the ester-forming ingredients comprising 80%-100%, by weight, of said polycster-polyamide.

2. A heat-softening stiffening member for shoes and the like, said member comprising a porous fabric impregnated with 300% to 900%, by weight of said fabric, of a polyester-polyamide derived from the inter-reaction of decamethylene diamine, ethylene glycol and sebacic acid, the

ester-forming ingredients comprising 85% 6 by weight, of said polyester-polyamide.

3. A heat-softening stiffening member for shoes and the like, said member comprising 2 porous fabric impregnated with 300% to 900%. by weight of said fabric, of a polyester-polyamide derived from the inter-reaction of hexamethylene diamine, ethylene glycol, and sebaoic acid, the

5 ester-forming ingredients comprising 85 %-100%,

by weight, of said polyester-polyamide.

' 4. A' heat-softening stiffening member for shoes and the like, said member comprising a porous fabric impregnated with 300% to 900%, by weight of said fabric, of a polyester-polyamide derived from the inter-reaction of hexamethylene diamine, ethylene glycol and adipic acid, the ester-forming ingredients comprising 82%95%, by weight, of said polyester-polyamide.

5. Process of preparing a heat-softening stiffening material for shoes and the like, which process comprises introducing a porous fabric into a solution of a polyester-polyamide in a volatile solvent therefor to impregnate said fabric with said solution, removing said fabric, thus impregnated, from said solution, stripping from the surface of said fabric excess of said solution above that required to leave 300% to 900%, by weight of said fabric, of said polyester-polyamide as an impregnant in said fabric after removal of said volatile solvent, and removing said volatile solvent from said impregnated fabric, said polyester-polyamide being derived from the interreaction of a diamlne of the formula R representing a saturated divalent aliphatic hydrocarbon radical of six to ten carbon atoms, inclusive, a dibasic acid of the formula R representing a saturated divalent aliphatic hydrocarbon radical of four to eight carbon atoms, inclusive, and a glycol having two to three carbon atoms, inclusive, per molecule, the esterforming ingredients comprising 80%l00%, by weight, of said polyester-polyamide.

6. Process of preparing a heat-softening stiffening material for shoes and the like, which process comprises passing a continuous Web of porous fabric through a hot solution of a polyester-polyamide in a volatile solvent therefor to impregnate said fabric with said solution, con tinuously stripping from the surface of said fabric excess of said solution above that required to leave 300% to 900%, by weight of said fabric, of said polyester-polyamide as an impregnant in said fabric after removal of said volatile solvent. and removing said volatile solvent from said impregnated fabric, said polyester-polyamide being derived from the inter-reaction of a diamine of the formula NH2RNH2, R representing a saturated divalent aliphatic hydrocarbon radical of six to ten carbon atoms, inclusive, a dibasic acid of the formula HOOCR'-COOH, R representing a saturated divalent aliphatic hydrocarbon radical of four to eight carbon atoms, inclusive, and a glycol having two to three carbon atoms, inclusive, per molecule, the ester-forming ingredients comprising 80% to 100%, by weight, of said polyester polyamide.

PAUL R. AUSTIN. QUENTIN L. QUINLIVAN. 

